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Abstract:

A touch pad with an antenna includes a substrate on an upper side of
which an operation surface having a predetermined operation region is
set, an electrode group for detecting capacitance configured to be
arranged in a region of the substrate corresponding to the operation
region, and an antenna for wireless communication configured to be
arranged in a region located on a lower side of the substrate, the region
overlapping with an electrode forming region in which the electrode group
for detecting capacitance is formed, as viewed from above. The electrode
group for detecting capacitance includes a first electrode group extended
in a predetermined first direction and a second electrode group extended
in a second direction perpendicular to the first direction, and the
antenna is extended in a direction intersecting with the first direction
and the second direction.

Claims:

1. A touch pad with an antenna comprising: a substrate on an upper side
of having set thereon an operation surface having a predetermined
operation region; an electrode group that detects capacitance arranged in
a region of the substrate corresponding to the operation region; and an
antenna for wireless communication arranged in a region located on a
lower side of the substrate, the region overlapping with an electrode
group forming region in which the electrode group for detecting
capacitance is disposed, as viewed from above, wherein the electrode
group for detecting capacitance includes a first electrode group extended
in a predetermined first direction and a second electrode group extended
in a second direction perpendicular to the first direction, and wherein
the antenna is extended in a direction intersecting with the first
direction and the second direction.

2. The touch pad with an antenna according to claim 1, wherein the
antenna comprises a coiled antenna wound along an outer circumference of
a circle.

3. The touch pad with an antenna according to claim 1, wherein the
operation region is a rectangular-shaped region having a long side
extending in the first direction and a short side extending in the second
direction, and the antenna comprises a coiled antenna wound along an
outer circumference of an ellipse having a long axis extending in the
first direction and a short axis extending in the second direction.

4. The touch pad with an antenna according to claim 1, wherein a ground
electrode made of a conductive material is arranged at a position,
located on a lower side of the electrode group for detecting capacitance
and located on an upper side of the antenna, so as to overlap with a
whole region of the electrode forming region as viewed from above, and a
plurality of slits are formed in the ground electrode so as to radially
extend from the vicinity of a central portion of the ground electrode.

5. The touch pad with an antenna according to claim 4, wherein the slits
are arranged at regular intervals with respect to a rotation direction
centered at the central portion of the ground electrode.

6. The touch pad with an antenna according to claim 4, wherein the slits
are formed so as to divide an outer periphery portion of the ground
electrode.

7. The touch pad with an antenna according to claim 4, wherein the ground
electrode includes a linking portion configured to link a plurality of
ground electrode patterns divided by the slits, in the central portion of
the ground electrode.

Description:

CLAIM OF PRIORITY

[0001] This application claims benefit of Japanese Patent Application No.
2014-001163 filed on Jan. 7, 2014, which is hereby incorporated by
reference in its entirety.

BACKGROUND

[0002] 1. Field of the Disclosure

[0003] The present disclosure relates to a touch pad with an antenna, and
in particular, relates to a touch pad with an antenna, used for wireless
communication.

[0004] 2. Description of the Related Art

[0005] Touch pads in each of which the position of an operation body in
contact with or close to an operation surface is detectable have become
very popular, and have been used for moving cursors of screens of
electronic devices such as notebook computers. The touch pads are each
attached to an opening portion formed in a predetermined location (a palm
rest or the like) of a chassis covering the main body of an electronic
device such as a notebook computer.

[0006] The opening portion to which the touch pad is attached is used for
radiating, to the outside of the electronic device, a wireless signal
(electromagnetic wave signal) generated by a communication circuit on an
electronic device side. In addition, in recent years, touch pads with
antennas, in each of which an antenna for wireless communication
connected to such a communication circuit is integrated with a touch pad,
have been put into practical use.

[0007] As a touch pad with an antenna of the related art, a touch pad
module (touch pad with an antenna) according to Japanese Unexamined
Patent Application Publication (Translation of PCT Application) No.
2002-539517 has been proposed. FIGS. 11A and 11B are explanatory diagrams
illustrating the configuration of a touch pad module 200 according to
Japanese Unexamined Patent Application Publication (Translation of PCT
Application) No. 2002-539517. FIG. 11A is an explanatory diagram
schematically illustrating the side cross-section of the touch pad module
200. FIG. 11B is an explanatory diagram schematically illustrating the
lower surface of a printed circuit board 220 used in the touch pad module
200.

[0008] The touch pad module 200 is a capacitive (electrostatic capacitance
type) touch pad. As illustrated in FIGS. 11A and 11B, the touch pad
module 200 includes the printed circuit board 220 having a nearly
rectangular-shaped plate surface, and a touch sensor array 222 including
a plurality of layers formed in the upper portion of the printed circuit
board 220.

[0009] In a portion situated nearer to the center of a lower surface 224
serving as one plate surface of the printed circuit board 220, a chip
226, a chip 228, a configuration element 230, a configuration element
232, a configuration element 234, and so forth are mounted, and configure
a circuit unit having a predetermined function. The circuit unit is
connected to the touch sensor array 222 through wiring lines not
illustrated. In addition, in the outer periphery portion of the lower
surface 224 of the printed circuit board 220, an antenna 236 for wireless
communication is formed. The antenna 236 is extended along the outer
circumference of the lower surface 224 of the printed circuit board 220.

[0010] Note that while the detailed structure of the touch sensor array
222 is not disclosed in Japanese Unexamined Patent Application
Publication (Translation of PCT Application) No. 2002-539517, usually the
touch sensor array of the capacitive touch pad includes a first electrode
group extended in the long-side direction of a board having a nearly
rectangular-shaped plate surface, and a second electrode group extended
in the short-side direction thereof. In addition, based on a change in
electrostatic capacitance detected using the first electrode group and
the second electrode group, the position of an operation body in contact
with or close to the operation surface of the touch pad is detected.

[0011] In the touch pad module 200 according to Japanese Unexamined Patent
Application Publication (Translation of PCT Application) No. 2002-539517,
the antenna 236 is extended along the outer circumference of the nearly
rectangular-shaped plate surface of the printed circuit board 220. In
addition, as described above, usually the touch sensor array of the
capacitive touch pad includes the first electrode group extended in the
long-side direction of the board having the nearly rectangular-shaped
plate surface, and the second electrode group extended in the short-side
direction thereof. Therefore, a large portion of the antenna 236 in the
extension direction thereof is headed in a direction parallel to the
extension direction of the first electrode group or the second electrode
group.

[0012] In a point at which the extension direction of the antenna 236 is
parallel to the extension direction of the first electrode group or the
second electrode group, magnetic field coupling caused by mutual
induction is easily produced between the antenna 236 and the first
electrode group or the second electrode group. In addition, by magnetic
field coupling between the antenna 236 and the first electrode group or
the second electrode group, a magnetic field generated by the antenna 236
is easily transmitted, as a noise, to the first electrode group or the
second electrode group. As a result, in such a structure as the touch pad
module 200 according to Japanese Unexamined Patent Application
Publication (Translation of PCT Application) No. 2002-539517, there has
been a possibility that, under the influence of the noise due to the
antenna 236, detection accuracy at the time of detecting the position of
an operation body in contact with or close to an operation surface is
reduced.

[0013] The present invention is made in view of such a situation of the
related art, and provides a touch pad with an antenna, capable of
reducing the influence of a noise due to the antenna.

SUMMARY

[0014] According to a first aspect of the present invention, a touch pad
with an antenna includes a substrate on an upper side of having set
thereon an operation surface having a predetermined operation region, an
electrode group that detects capacitance arranged in a region of the
substrate corresponding to the operation region, and an antenna for
wireless communication arranged in a region located on a lower side of
the substrate, the region overlapping with an electrode group forming
region in which the electrode group for detecting capacitance is
disposed, as viewed from above, wherein the electrode group for detecting
capacitance includes a first electrode group extended in a predetermined
first direction and a second electrode group extended in a second
direction perpendicular to the first direction, and the antenna is
extended in a direction intersecting with the first direction and the
second direction.

[0015] In the touch pad with an antenna having this configuration, the
first electrode group is extended in the first direction, and the antenna
is extended in the direction intersecting with (a direction not parallel
to) the first direction. Therefore, it is possible to suppress magnetic
field coupling due to mutual induction between the antenna and the first
electrode group. In addition, it is possible to inhibit a magnetic field
generated by the antenna from being transmitted, as a noise, to the first
electrode group. In addition, the second electrode group is extended in
the second direction, and the antenna is extended in the direction
intersecting with (a direction not parallel to) the second direction.
Therefore, it is possible to suppress magnetic field coupling due to
mutual induction between the antenna and the second electrode group. In
addition, it is possible to inhibit the magnetic field generated by the
antenna from being transmitted, as a noise, to the second electrode
group. As a result, the touch pad with an antenna having this
configuration is able to reduce the influence of a noise due to the
antenna.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIGS. 1A and 1B are explanatory diagrams illustrating a
configuration of a touch pad according to a first embodiment of the
present invention;

[0017] FIG. 2 is an explanatory diagram illustrating a usage example of
the touch pad illustrated in FIGS. 1A and 1B;

[0018] FIG. 3 is an exploded perspective view of the touch pad illustrated
in FIGS. 1A and 1B;

[0019] FIGS. 4A and 4B are first explanatory diagrams illustrating
electrode geometries of a substrate illustrated in FIGS. 1A and 1B;

[0020] FIGS. 5A and 5B are second explanatory diagrams illustrating
electrode geometries of the substrate illustrated in FIGS. 1A and 1B;

[0021] FIGS. 6A and 6B are explanatory diagrams illustrating a function of
an antenna illustrated in FIG. 3;

[0022] FIG. 7 is an explanatory diagram illustrating a function of a
ground electrode illustrated in FIG. 3;

[0023] FIGS. 8A and 8B are explanatory diagrams illustrating a
configuration of a touch pad according to a second embodiment of the
present invention;

[0024] FIGS. 9A and 9B are first explanatory diagrams illustrating
electrode geometries of a substrate illustrated in FIGS. 8A and 8B;

[0025] FIGS. 10A and 10B are second explanatory diagrams illustrating
electrode geometries of the substrate illustrated in FIGS. 8A and 8B; and

[0026] FIGS. 11A and 11B are explanatory diagrams illustrating a
configuration of a touch pad module according to Japanese Unexamined
Patent Application Publication (Translation of PCT Application) No.
2002-539517.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

First Embodiment

[0027] Hereinafter, a first embodiment of the present invention will be
described with reference to drawings. Note that it is assumed that, in
each drawing, an X1 direction is a left direction, an X2 direction is a
right direction, a Y1 direction is an anterior direction, a Y2 direction
is a posterior direction, a Z1 direction is an upper direction, and a Z2
direction is a lower direction and an explanation will be made.

[0028] First, the configuration of a touch pad 1 (a touch pad with an
antenna) according to the first embodiment of the present invention will
be described using FIG. 1A to FIG. 5B. FIGS. 1A and 1B are explanatory
diagrams illustrating the configuration of the touch pad 1 according to
the first embodiment of the present invention. FIG. 2 is an explanatory
diagram illustrating a usage example of the touch pad 1 illustrated in
FIGS. 1A and 1B. FIG. 3 is the exploded perspective view of the touch pad
1 illustrated in FIGS. 1A and 1B. FIGS. 4A and 4B are first explanatory
diagrams illustrating the electrode geometries of a substrate 20
illustrated in FIGS. 1A and 1B. FIG. 4A is an explanatory diagram
illustrating the electrode geometry of a first electrode group 25, and
FIG. 4B is an explanatory diagram illustrating the electrode geometry of
a second electrode group 26. FIGS. 5A and 5B are second explanatory
diagrams illustrating the electrode geometries of the substrate 20
illustrated in FIGS. 1A and 1B. FIG. 5A is an explanatory diagram
illustrating the electrode geometry of a ground electrode 27, and FIG. 5B
is an explanatory diagram illustrating the electrode geometry of an
antenna 28.

[0029] The touch pad 1 is a touch pad of a type called an electrostatic
capacitance type. As illustrated in FIGS. 1A and 1B, the touch pad 1
includes an operation plate 10 with an operation surface 11 on the upper
side thereof, and the substrate 20 arranged on the lower side of the
operation plate 10. In addition, the touch pad 1 is able to detect the
position of an operation body such as a fingertip in contact with or
close to the operation surface 11. As illustrated in FIG. 2, such a touch
pad 1 is attached to a predetermined location (a palm rest or the like)
of a chassis 51 of an electronic device 50 such as a notebook computer so
that the operation surface 11 is exposed, and the touch pad 1 is used for
moving a cursor of a screen, or the like.

[0030] The operation plate 10 is a plate-like member made of a synthetic
resin, and includes nearly rectangular-shaped plate surfaces on the top
and bottom thereof. As illustrated in FIG. 3, the top surface of the
operation plate 10 is the operation surface 11, and a predetermined
region of the operation surface 11 is an operation region 11a. In the
present embodiment, the operation region 1 1a is a square-shaped region
having sides extending in a first direction on the operation surface 11
and a second direction perpendicular to the first direction. As
illustrated in FIG. 3, the first direction is a horizontal direction, and
the second direction is a front-back direction.

[0031] The substrate 20 is a multilayer substrate made of a synthetic
resin, and includes nearly rectangular-shaped plate surfaces on the top
and bottom thereof. As illustrated in FIG. 3, the substrate 20 includes
four electrode forming layers of a first electrode forming layer 21, a
second electrode forming layer 22, a ground electrode forming layer 23,
and an antenna forming layer 24. Predetermined electrodes made of a
conductive material such as copper are formed in the first electrode
forming layer 21, the second electrode forming layer 22, the ground
electrode forming layer 23, and the antenna forming layer 24.

[0032] The first electrode forming layer 21, the second electrode forming
layer 22, the ground electrode forming layer 23, and the antenna forming
layer 24 are stacked with sandwiching therebetween insulation layers not
illustrated, in the order of the first electrode forming layer 21, the
second electrode forming layer 22, the ground electrode forming layer 23,
and the antenna forming layer 24 starting from the top. In addition, the
first electrode forming layer 21 is the top surface of the substrate 20,
and the antenna forming layer 24 is the bottom surface of the substrate
20. The upper side of the first electrode forming layer 21 and the lower
side of the antenna forming layer 24 are covered by insulating coatings
not illustrated.

[0033] In the first electrode forming layer 21 of the substrate 20, the
first electrode group 25 serving as a first electrode group for detecting
capacitance is formed. The first electrode group 25 is formed in the
inside of a first electrode forming region 21a serving as a square-shaped
region overlapping with the operation region 11a as viewed from above.
The first electrode group 25 includes a plurality of first electrodes
25a. As illustrated in FIGS. 4A and 4B, each of the first electrodes 25a
is a nearly rectangular-shaped electrode extended in the first direction.
The first electrodes 25a may be arranged so as to be placed at regular
intervals in the second direction. Note that, in the present embodiment,
the first electrodes 25a of the first electrode group 25 are used as
drive electrodes, and an electric signal for driving is applied to each
of the first electrodes 25a.

[0034] In the second electrode forming layer 22 of the substrate 20, the
second electrode group 26 serving as a second electrode group for
detecting capacitance is formed. The second electrode group 26 is formed
in the inside of a second electrode forming region 22a serving as a
square-shaped region overlapping with the operation region 11a as viewed
from above. The second electrode group 26 includes a plurality of second
electrodes 26a. As illustrated in FIGS. 4A and 4B, each of the second
electrodes 26a is a nearly rectangular-shaped electrode extended in the
second direction. The second electrodes 26a may be arranged so as to be
placed at regular intervals in the first direction. Note that, in the
present embodiment, the second electrodes 26a of the second electrode
group 26 are used as detection electrodes.

[0035] The first electrodes 25a of the first electrode group 25 and the
second electrodes 26a of the second electrode group 26 are arranged so as
to intersect with each other as viewed from above. In addition, one of
the first electrodes 25a and a corresponding one of the second electrodes
26a form electrostatic capacitance in the vicinity of a position at which
one of the first electrodes 25a and the corresponding one of the second
electrodes 26a intersect with each other. In addition, by the
electrostatic capacitance between one of the first electrodes 25a and the
corresponding one of the second electrodes 26a, the electric signal for
driving applied to one of the first electrodes 25a is transmitted from
one of the first electrodes 25a to the corresponding one of the
corresponding second electrodes 26a. In the touch pad 1, based on a
change in the electric signal transmitted from one of the first
electrodes 25a to the corresponding one of the corresponding second
electrodes 26a in this way, it is possible to detect a change in the
electrostatic capacitance between one of the first electrodes 25a and the
corresponding one of the second electrodes 26a.

[0036] The ground electrode 27 is formed in the ground electrode forming
layer 23 of the substrate 20. The ground electrode 27 may be formed in
the inside of a ground electrode forming region 23a serving as a
square-shaped region overlapping with the whole regions of the first
electrode forming region 21a and the second electrode forming region 22a
as viewed from above.

[0037] As illustrated in FIGS. 5A and 5B, the ground electrode 27 may be
formed by adding a plurality of slits 27a to a square-shaped electrode
covering the whole region of the ground electrode forming region 23a. The
slits 27a may be arranged at regular intervals in a rotation direction
centered at the central portion of the ground electrode 27. In addition,
the slits 27a may each radially extend from the vicinity of the central
portion of the ground electrode 27 to the outer periphery portion
thereof. The outer periphery portion of the ground electrode 27 may be
divided into a plurality of ground electrode patterns 27b by the slits
27a. The central portion of the ground electrode 27 may be a linking
portion 27c linking the ground electrode patterns 27b divided by the
slits 27a.

[0038] In the antenna forming layer 24 of the substrate 20, an electrode
pattern to serve as the antenna 28 for wireless communication is formed.
Hereinafter, the electrode pattern to serve as the antenna 28 for
wireless communication is abbreviated as the antenna 28. The antenna 28
is formed in the inside of an antenna forming region 24a serving as a
square-shaped region overlapping with the first electrode forming region
21a and the second electrode forming region 22a as viewed from above.

[0039] As illustrated in FIGS. 5A and 5B, the antenna 28 may be a coiled
(spiral-coil-shaped) antenna wound along the outer circumference of a
circle sharing the center thereof with the antenna forming region 24a.
Two end portions of the antenna 28 are terminal portions 28a connected to
a circuit.

[0040] A region on the left side of the antenna forming region 24a and a
region on the right side thereof in the antenna forming layer 24 are
circuit forming regions 24b in which predetermined circuits are formed.
In the circuit forming regions 24b, various kinds of electronic
components not illustrated are mounted and a detection circuit 30 for
detecting the position of the operation body in contact with or close to
the operation surface 11, a communication circuit 40 for wireless
communication, and so forth are formed.

[0041] The detection circuit 30 is connected to the first electrode group
25 and the second electrode group 26, described above, through electrodes
for wiring lines, not illustrated. The detection circuit 30 applies an
electric signal for driving to each of the first electrodes 25a of the
first electrode group 25, detects an electric signal transmitted to a
corresponding one of the second electrodes 26a of the second electrode
groups 26, and detects, based on a change in an electric signal
transmitted from one of the first electrodes 25a to a corresponding one
of the second electrodes 26a, a change in electrostatic capacitance
between one of the first electrodes 25a and the corresponding one of the
second electrodes 26a. In addition, based on a change in the
electrostatic capacitance detected using the first electrode group 25 and
the second electrode group 26, the detection circuit 30 detects the
position of the operation body in contact with or close to the operation
surface 11 of the touch pad 1. Note that since the circuit configuration
and so forth of such a detection circuit 30 are publicly known, the
detailed descriptions thereof will be omitted.

[0042] The communication circuit 40 is a communication circuit compatible
with the standard of short distance wireless communication. The
communication circuit 40 is connected to the terminal portions 28a of the
antenna 28 through electrodes for wiring lines not illustrated. In
addition, the communication circuit 40 applies an electric signal for
wireless communication to the terminal portions 28a of the antenna 28.
Note that since the circuit configuration of such a communication circuit
40 is publicly known, the detailed description thereof will be omitted.

[0043] The substrate 20 has such a configuration as described above. In
addition, the operation plate 10 is stuck on the upper side of such a
substrate 20 using an adhesive or the like. As a result, the operation
surface 11 having the predetermined operation region 11a is set on the
upper side of the substrate 20.

[0044] Next, the function of the antenna 28 will be described using FIGS.
6A and 6B. FIGS. 6A and 6B are explanatory diagrams illustrating the
function of the antenna 28 illustrated in FIG. 3. FIG. 6A is an
explanatory diagram schematically illustrating the radiation direction Ra
of a magnetic flux generated by the antenna 28 in a case of viewing the
antenna 28 from above along with the first electrode group 25. FIG. 6B is
an explanatory diagram schematically illustrating the radiation direction
Ra of the magnetic flux generated by the antenna 28 in a case of viewing
the antenna 28 from above along with the second electrode group 26.

[0045] When the electric signal for wireless communication is applied to
the terminal portions 28a of the antenna 28, a current corresponding to
the applied electric signal flows through the antenna 28, and a magnetic
flux is generated in a direction perpendicular to the current flowing
through the antenna 28. In addition, in response to the magnetic flux
generated by the antenna 28, a magnetic field is formed around the
antenna 28. In FIGS. 6A and 6B, the magnetic flux generated by the
antenna 28 is radiated in a direction from the center of the antenna
forming region 24a toward the outer side portion thereof. In addition, a
magnetic field distribution approximately rotationally symmetrical to the
center of the antenna forming region 24a is formed. Using the magnetic
field formed in this way, the antenna 28 performs transmission and
reception of signals to and from an external communication device not
illustrated.

[0046] Note that, as will be appreciated from the above-mentioned
configuration of the touch pad 1, the first electrode group 25 is
arranged on the upper side of the antenna 28. The first electrodes 25a of
the first electrode group 25 are extended in the first direction, as
illustrated in FIG. 6A. In a case where the antenna 28 is extended in,
for example, the first direction (a direction parallel to the extension
direction of the first electrodes 25a) with respect to such first
electrodes 25a, magnetic field coupling due to mutual induction is easily
produced between the antenna 28 and a corresponding one of the first
electrodes 25a at a point at which the extension direction of the antenna
28 and the extension direction of the corresponding one of the first
electrodes 25a are parallel to each other. The strength of the magnetic
field coupling between the antenna 28 and the corresponding one of the
first electrodes 25a increases with an increase in the length of the
point at which the extension direction of the antenna 28 and the
extension direction of the corresponding one of the first electrodes 25a
are parallel to each other.

[0047] In addition, by the magnetic field coupling between the antenna 28
and the corresponding one of the first electrodes 25a, a magnetic field
generated by the antenna 28 is caused to be easily transmitted to the
corresponding one of the first electrodes 25a, as a noise. As a result,
there is a possibility that, under the influence of the noise due to the
antenna 28, detection accuracy at the time of detecting the position of
the operation body in contact with or close to the operation surface is
reduced.

[0048] However, the antenna 28 may be a coiled antenna wound along the
outer circumference of a circle sharing the center thereof with the
antenna forming region 24a, and there is hardly a point at which the
extension direction of the antenna 28 and the extension direction of a
corresponding one of the first electrodes 25a are parallel to each other.
Therefore, it is possible to suppress magnetic field coupling due to
mutual induction between the antenna 28 and the first electrodes 25a. In
addition, it is possible to inhibit the magnetic field generated by the
antenna 28 from being transmitted to the first electrodes 25a, as a
noise.

[0049] In addition, as will be appreciated from the above-mentioned
configuration of the touch pad 1, the second electrode group 26 is
arranged on the upper side of the antenna 28. The second electrodes 26a
of the second electrode group 26 are extended in the second direction, as
illustrated in FIG. 6B. In a case where the antenna 28 is extended in,
for example, the second direction (a direction parallel to the extension
direction of the second electrodes 26a) with respect to such second
electrodes 26a, magnetic field coupling due to mutual induction is easily
produced between the antenna 28 and a corresponding one of the second
electrodes 26a at a point at which the extension direction of the antenna
28 and the extension direction of the corresponding one of the second
electrodes 26a are parallel to each other. In addition, by the magnetic
field coupling between the antenna 28 and the corresponding one of the
second electrodes 26a, a magnetic field generated by the antenna 28 is
caused to be easily transmitted to the corresponding one of the second
electrodes 26a, as a noise.

[0050] However, the antenna 28 may be a coiled antenna wound along the
outer circumference of a circle sharing the center thereof with the
antenna forming region 24a, and there is hardly a point at which the
extension direction of the antenna 28 and the extension direction of a
corresponding one of the second electrodes 26a are parallel to each
other. Therefore, it is possible to suppress magnetic field coupling due
to mutual induction between the antenna 28 and the second electrodes 26a.
In addition, it is possible to inhibit the magnetic field generated by
the antenna 28 from being transmitted to the second electrodes 26a, as a
noise.

[0051] Note that the antenna 28 may be a coiled antenna wound along the
outer circumference of a circle. Therefore, strictly speaking, in the
vicinity of the anterior end portion of the antenna 28 and in the
vicinity of the posterior end portion thereof, there are points at which
the extension direction of the antenna 28 and the extension direction of
the first electrodes 25a are parallel to each other. However, since such
points each have no sufficient length, it is possible to regard the
antenna 28 as a coil extended in a direction intersecting with the
extension direction of the first electrodes 25a.

[0052] In addition, in the same way, in the vicinity of the left end
portion of the antenna 28 and in the vicinity of the right end portion
thereof, there are points at which the extension direction of the antenna
28 and the extension direction of the second electrodes 26a are parallel
to each other. However, since such points each have no sufficient length,
it is possible to regard the antenna 28 as a coil extended in a direction
intersecting with the extension direction of the second electrodes 26a.

[0053] Next, using FIG. 7, the function of the ground electrode 27 will be
described. FIG. 7 is an explanatory diagram illustrating the function of
the ground electrode 27 illustrated in FIG. 3. FIG. 7 is an explanatory
diagram schematically illustrating the radiation direction Ra of the
magnetic flux generated by the antenna 28 in a case of viewing the
antenna 28 from above along with the ground electrode 27.

[0054] As will be appreciated from the above-mentioned configuration of
the touch pad 1, the ground electrode 27 may be arranged at a position,
located on the lower side of the first electrode group 25 and the second
electrode group 26 and located on the upper side of the antenna 28. In
addition, the ground electrode 27 inhibits an electromagnetic wave noise
generated by the main body of the electronic device 50 from being
radiated to the outside of the electronic device 50, and inhibits the
magnetic field generated by the antenna 28 from being transmitted, as a
noise, to the first electrode group 25 and the second electrode group 26.

[0055] In addition, as illustrated in FIG. 7, the slits 27a may be formed
in the ground electrode 27. In addition, a signal for wireless
communication is radiated from the antenna 28 to the outside of the
electronic device 50 through the slits 27a. Furthermore, the slits 27a
may be arranged at regular intervals in the rotation direction centered
at the center of the ground electrode 27. In addition, the bias of the
signal with respect to the rotation direction centered at the center of
the ground electrode 27 is reduced, the signal being radiated from the
antenna 28 to the outside of the electronic device 50 through the slits
27a.

[0056] In addition, the slits 27a have a function for suppressing an eddy
current flowing through the ground electrode 27. In general, in a case
where the ground electrode 27 is arranged on the upper side of such a
coiled antenna as the antenna 28, an eddy current flows through the
ground electrode 27 in the extension direction of the antenna 28 in
response to the magnetic field generated by the antenna 28. In addition,
in connection with the eddy current flowing through the ground electrode
27, the loss of electric power is generated. In contrast, as illustrated
in FIG. 7, in the present embodiment, the slits 27a may be formed so as
to radially extend from the vicinity of the central portion of the ground
electrode 27, and such slits 27a suppress the eddy current flowing
through the ground electrode 27 in response to the magnetic field
generated by the antenna 28.

[0057] Note that the slits 27a may divide the outer periphery portion of
the ground electrode 27 into the ground electrode patterns 27b. Usually,
the antenna 28 is formed in the vicinity of the outer periphery portion
of the antenna forming region 24a. Therefore, the strength of the
magnetic field generated by the antenna 28 increases in the vicinity of
the outer periphery portion of the antenna forming region 24a, compared
with the vicinity of the central portion of the antenna forming region
24a. In response to that, the magnitude of an eddy current flowing
through the vicinity of the outer periphery portion of the ground
electrode 27 becomes larger than that of an eddy current flowing through
the vicinity of the central portion thereof. In addition, compared with
the path of the eddy current flowing through the vicinity of the central
portion of the ground electrode 27, the path of the eddy current flowing
through the vicinity of the outer periphery portion of the ground
electrode 27 is long. Therefore, compared with a loss due to the eddy
current flowing through the vicinity of the central portion of the ground
electrode 27, a loss due to the eddy current flowing through the vicinity
of the outer periphery portion thereof becomes large. Therefore, in a
case of forming the slits 27a, a case of forming the slits 27a so as to
divide the outer periphery portion of the ground electrode 27 obtains a
great advantageous effect compared with a case of forming the slits 27a
so as to divide the central portion of the ground electrode 27.

[0058] Next, advantageous effects of the present embodiment will be
described. In the touch pad 1 of the present embodiment, the first
electrodes 25a of the first electrode group 25 are extended in the first
direction (horizontal direction), and the antenna 28 is extended in a
direction intersecting with (a direction not parallel to) the first
direction. Therefore, it is possible to suppress magnetic field coupling
due to mutual induction between the antenna 28 and the first electrodes
25a of the first electrode group 25. In addition, it is possible to
inhibit the magnetic field generated by the antenna 28 from being
transmitted, as a noise, to the first electrodes 25a of the first
electrode group 25. In addition, the second electrodes 26a of the second
electrode group 26 are extended in the second direction (front-back
direction), and the antenna 28 is extended in a direction intersecting
with (a direction not parallel to) the second direction. Therefore, it is
possible to suppress magnetic field coupling due to mutual induction
between the antenna 28 and the second electrodes 26a of the second
electrode group 26. In addition, it is possible to inhibit the magnetic
field generated by the antenna 28 from being transmitted, as a noise, to
the second electrodes 26a of the second electrode group 26. As a result,
the touch pad 1 of this configuration is able to reduce the influence of
a noise due to the antenna 28.

[0059] In addition, in the touch pad 1 of the present embodiment, the
antenna 28 may be a coiled antenna wound along the outer circumference of
a circle. Therefore, the antenna 28 is able to form a magnetic field
approximately rotationally symmetrical to the center of the circle. As a
result, it is possible to reduce the bias of a communication sensitivity
with respect to a communication direction. In particular, the shape of
such an antenna 28 is effective for a touch pad having a square-shaped
operation region.

[0060] In addition, in the touch pad 1 of the present embodiment, using
the ground electrode 27 arranged at a position, located on the lower side
of the first electrode group 25 and the second electrode group 26 and
located on the upper side of the antenna 28, it is possible to inhibit
the electromagnetic wave noise generated by the main body of the
electronic device 50 from being radiated to the outside of the electronic
device 50, and it is possible to further inhibit the magnetic field
generated by the antenna 28 from being transmitted, as a noise, to the
first electrode group 25 and the second electrode group 26. Furthermore,
since the slits 27a may be formed in the ground electrode 27, it is
possible to radiate the signal for wireless communication from the
antenna 28 to the outside of the electronic device 50 through the slits
27a. In addition, since the slits 27a may radially extend from the
vicinity of the central portion of the ground electrode 27, it is
possible to suppress the eddy current flowing through the ground
electrode 27 in response to the magnetic field generated by the antenna
28. In addition, it is possible to reduce a loss associated with the eddy
current.

[0061] In addition, in the touch pad 1 of the present embodiment, the
slits 27a may be arranged at regular intervals in the rotation direction
centered at the center of the ground electrode 27. Therefore, it is
possible to reduce the bias of a signal with respect to the rotation
direction centered at the center of the ground electrode 27, the signal
being radiated from the antenna 28 to the outside of the electronic
device 50 through the slits 27a.

[0062] In addition, in the touch pad 1 of the present embodiment, the
slits 27a may be formed so as to divide the outer periphery portion of
the ground electrode 27. Therefore, it is possible to prevent the eddy
current from flowing through the vicinity of the outer periphery portion
of the ground electrode 27. As a result, it is possible to further
suppress the eddy current flowing through the ground electrode 27 in
response to the magnetic field generated by the antenna 28. In addition,
it is possible to further reduce a loss associated with the eddy current.

[0063] In addition, while, in the touch pad 1 of the present embodiment,
the outer periphery portion of the ground electrode 27 may be divided by
the slits 27a into the ground electrode patterns 27b, it is possible to
electrically connect the ground electrode patterns 27b using the linking
portion 27c. Therefore, it is possible to reduce the number of ground
wiring lines connected to the ground electrode 27, compared with a case
where the ground electrode patterns 27b are not linked to the linking
portion 27c. As a result, it is possible to simplify the structure of the
touch pad 1.

Second Embodiment

[0064] Hereinafter, a second embodiment of the present invention will be
described with reference to drawings. Note that, in the present
embodiment, in a case of the same configuration as that of the
above-mentioned first embodiment, a same symbol is assigned thereto and
the detailed description thereof will be omitted.

[0065] First, the configuration of a touch pad 101 (a touch pad with an
antenna) according to the second embodiment of the present invention will
be described using FIG. 8A to FIG. 10B. FIGS. 8A and 8B are explanatory
diagrams illustrating the configuration of the touch pad 101 according to
the second embodiment of the present invention. FIGS. 9A and 9B are first
explanatory diagrams illustrating the electrode geometries of a substrate
120 illustrated in FIGS. 8A and 8B. FIG. 9A is an explanatory diagram
illustrating the electrode geometry of the first electrode group 25, and
FIG. 9B is an explanatory diagram illustrating the electrode geometry of
the second electrode group 26. FIGS. 10A and 10B are second explanatory
diagrams illustrating the electrode geometries of the substrate 120
illustrated in FIGS. 8A and 8B. FIG. 10A is an explanatory diagram
illustrating the electrode geometry of the ground electrode 27, and FIG.
10B is an explanatory diagram illustrating the electrode geometry of an
antenna 128.

[0066] In the same way as the touch pad 1 of the first embodiment, the
touch pad 101 is a touch pad of a type called an electrostatic
capacitance type. As illustrated in FIGS. 8A and 8B, the touch pad 101
includes an operation plate 110, and the substrate 120 arranged on the
lower side of the operation plate 110. In addition, the top surface of
the operation plate 110 is the operation surface 11, and a predetermined
region of the operation surface 11 is the operation region 11a. In this
regard, however, in the present embodiment, the operation region 11a may
be a rectangular-shaped region having long sides extending in the first
direction on the operation surface 11 and short sides extending in the
second direction perpendicular to the first direction. While not
illustrated, the substrate 120 includes four electrode forming layers of
the first electrode forming layer 21, the second electrode forming layer
22, the ground electrode forming layer 23, and the antenna forming layer
24, in the same way as the substrate 20 of the first embodiment.

[0067] In the first electrode forming layer 21 of the substrate 120, the
first electrode group 25 is formed in the same way as the first
embodiment. In this regard, however, as illustrated in FIGS. 9A and 9B,
the first electrode forming region 21a of the first electrode forming
layer 21 is a rectangular-shaped region overlapping with the operation
region 11a as viewed from above. In the second electrode forming layer 22
of the substrate 120, the second electrode group 26 is formed in the same
way as the first embodiment. In this regard, however, as illustrated in
FIGS. 9A and 9B, the second electrode forming region 22a of the second
electrode forming layer 22 is a rectangular-shaped region overlapping
with the operation region 11a as viewed from above.

[0068] In the ground electrode forming layer 23 of the substrate 120, the
ground electrode 27 is formed in the same way as the first embodiment. In
this regard, however, as illustrated in FIGS. 10A and 10B, the ground
electrode forming region 23a of the ground electrode forming layer 23 is
a rectangular-shaped region overlapping the whole regions of the first
electrode forming region 21a and the second electrode forming region 22a
as viewed from above. In addition, the ground electrode 27 may be formed
by adding the slits 27a to a nearly rectangular-shaped electrode covering
the whole region of the ground electrode forming region 23a.

[0069] In the antenna forming layer 24 of the substrate 120, not the
antenna 28 but the antenna 128 is formed as illustrated in FIGS. 10A and
10B. In addition, the antenna forming region 24a of the antenna forming
layer 24 is a rectangular-shaped region overlapping with the first
electrode forming region 21a and the second electrode forming region 22a
as viewed from above. The antenna 128 may be a coiled
(spiral-coil-shaped) antenna wound along the outer circumference of an
ellipse having a long axis extending in the first direction and a short
axis extending in the second direction. The outside dimension of the
antenna 128 is set so that distances from the outer periphery portion of
the operation region 11a to the antenna 128 in a long-side direction and
a short-side direction become approximately equal to each other. Two end
portions of the antenna 128 are terminal portions 128a connected to a
circuit.

[0070] Next, advantageous effects of the present embodiment will be
described. In the touch pad 101 of the present embodiment, the first
electrodes 25a of the first electrode group 25 are extended in the first
direction (horizontal direction), and the antenna 128 is extended in a
direction intersecting with (a direction not parallel to) the first
direction. Therefore, it is possible to suppress magnetic field coupling
due to mutual induction between the antenna 128 and the first electrodes
25a of the first electrode group 25. In addition, it is possible to
inhibit a magnetic field generated by the antenna 128 from being
transmitted, as a noise, to the first electrodes 25a of the first
electrode group 25. In addition, the second electrodes 26a of the second
electrode group. 26 are extended in the second direction (front-back
direction), and the antenna 128 is extended in a direction intersecting
with (a direction not parallel to) the second direction. Therefore, it is
possible to suppress magnetic field coupling due to mutual induction
between the antenna 128 and the second electrodes 26a of the second
electrode group 26. In addition, it is possible to inhibit the magnetic
field generated by the antenna 128 from being transmitted, as a noise, to
the second electrodes 26a of the second electrode group 26. As a result,
the touch pad 101 of this configuration is able to reduce the influence
of a noise due to the antenna 128.

[0071] In addition, depending on the application or standard of the
electronic device 50, there is a case where a touch pad having not a
square-shaped operation region but a rectangular-shaped operation region
in such a manner as the touch pad 101 is used. In a case where, with
respect to such a touch pad, the antenna 128 is, for example, a coiled
antenna wound along the outer circumference of a circle, distances from
the outer periphery portion of the operation region 11a to the antenna
128 in the long-side direction and the short-side direction are different
from each other. As a result, there is a possibility that the bias of the
communication sensitivity with respect to the communication direction is
produced even if distances from the outer periphery portion of the
operation region 11a are equal to each other.

[0072] However, in the touch pad 101 of the present embodiment, the
operation region 11a may be the rectangular-shaped region having the long
sides extending in the first direction (horizontal direction) and the
short sides extending in the second direction (front-back direction), and
the antenna 128 may be the coiled antenna wound along the outer
circumference of the ellipse having the long axis extending in the first
direction and the short axis extending in the second direction.
Therefore, compared with a case where the antenna 128 is the coiled
antenna wound along the outer circumference of a circle, it is possible
to reduce the bias of a distance from the outer periphery portion of the
operation region 11a to the antenna 128. As a result, even in a case of a
touch pad having the rectangular-shaped operation region 11a in such a
manner as the touch pad 101, it is possible to reduce the bias of the
communication sensitivity with respect to the communication direction.

[0073] While embodiments of the present invention are described as above,
the present invention is not limited to the above-mentioned embodiments,
and may be arbitrarily modified without departing from the scope of
purposes of the present invention.

[0074] For example, in an embodiment of the present invention, an
electronic device to which the touch pad 1 (or the touch pad 101) is to
be attached may be a device other than the notebook computer. The touch
pad 1 (or the touch pad 101) may be used as an input device such as, for
example, a game machine or an in-vehicle navigation device.

[0075] In addition, in an embodiment of the present invention, the touch
pad 1 (or the touch pad 101) may include a member other than the
above-mentioned members. The touch pad 1 (or the touch pad 101) may
include, for example, a supporting member for swingably attaching itself
to an electronic device. In addition, a push switch or the like for
detecting the swinging operation of the touch pad 1 (or the touch pad
101) may be attached to the bottom surface of the substrate 20 (or the
substrate 120). In addition, the touch pad 1 (or the touch pad 101) may
include an attaching structure for attaching itself to the chassis of the
electronic device 50.

[0076] In addition, in an embodiment of the present invention, the
operation region 11a may have a shape other than the above-mentioned
shapes. A corner portion of the square shape (or the rectangular shape)
of the operation region 11a may have, for example, a circular arc shape.
In addition, if it is possible to detect the position of the operation
body in contact with or close to the operation surface 11 with
predetermined accuracy, the operation region 11a may be a circular-shaped
or elliptical-shaped region.

[0077] In addition, in an embodiment of the present invention, the
substrate 20 (or the substrate 120) is allowed not to include the circuit
forming region 24b, and the touch pad 1 (or the touch pad 101) is allowed
not to include the detection circuit 30 or the communication circuit 40.
In addition, the first electrode group 25 and the second electrode group
26 may be connected to, for example, a detection circuit and a
communication circuit, formed on the main body side of the electronic
device 50, through wiring lines or the like.

[0078] In addition, in an embodiment of the present invention, the first
electrodes 25a of the first electrode group 25 and the second electrodes
26a of the second electrode group 26 may each have a shape other than a
rectangular shape. The first electrodes 25a may be electrodes in which,
for example, a plurality of rhomboid-shaped electrodes linked to each
other are arranged so as to be placed alongside each other in the first
direction. In addition, the second electrodes 26a may be electrodes in
which a plurality of rhomboid-shaped electrodes linked to each other are
arranged so as to be placed alongside each other in the second direction.

[0079] In addition, while, in the embodiments of the present invention,
the first electrodes 25a of the first electrode group 25 are used as
drive electrodes and the second electrodes 26a of the second electrode
group 26 are used as detection electrodes, the second electrodes 26a may
be used as drive electrodes and the first electrodes 25a may be used as
detection electrodes. In addition, a state in which the first electrodes
25a are used as drive electrodes and the second electrodes 26a are used
as detection electrodes and a state in which the second electrodes 26a
are used as drive electrodes and the first electrodes 25a are used as
detection electrodes may be alternately switched depending on the timing
of detection. In addition, the touch pad 1 (or the touch pad 101) may
include an electrode to serve as a detection electrode other than the
first electrodes 25a and the second electrodes 26a, and may use the first
electrodes 25a and the second electrodes 26a as drive electrodes.

[0080] In addition, in an embodiment of the present invention, the antenna
28 (or the antenna 128) may have a shape other than the above-mentioned
shapes. If being able to realize a predetermined communication function,
the antenna 28 (or the antenna 128) may be, for example, a linear antenna
extended in a direction intersecting with the first direction and the
second direction. In addition, the antenna 28 (or the antenna 128) may be
a coiled (spiral-coil-shaped) antenna wound along the external form of a
rhomboid having sides extending in a direction intersecting with the
first direction and the second direction.

[0081] In addition, in an embodiment of the present invention, the antenna
28 (or the antenna 128) may be arranged on the lower side of the
substrate 20 (or the substrate 120) after being formed in a sheet-like
member different from the substrate 20 (or the substrate 120). In
addition, a magnetic sheet for suppressing the influence of a magnetic
field on the main body of the electronic device 50, a supporting plate
for supporting the touch pad 1 from below, or the like may be arranged on
the lower side of the antenna 28 (or the antenna 128).